In connection with the early diagnosis of lesions of the urinary tract, e.g., in the search for neoplasms and stone formation in the kidney and urogenital region, microhematurias have assumed ever increasing importance. Test strips which take advantage of the pseudoperoxidative activity of hemoglobin for the test reaction have proved to be most suitable as a mass screening test and, hence, are equally suitable for the detection of free hemoglobin of already lyzed erythrocytes and for intact erythrocytes (with the lysis occurring on the test field).
Diagnostic agents, more particularly in the form of test strips, for the detection of microhematurias are old in the art. Usually, they consist of an absorbent carrier made from fibrous or non-woven material, in the simplest case, filter paper, and which is impregnated with the detection reagents. The essential components of the detection reagent are a chromogen as an indicator, an oxidizing agent for the indicator, usually a hydroperoxide and an activator, sometimes also called a sensitizer or an accelerator, which increases the sensitivity of the detection. As a rule, other components are, apart from a surface-active agent (wetting agent), thickening agents which prevent the bleeding of the wetted test field, pigments, complex-forming agents and/or other stabilizers for chromogen and/or hydroperoxide.
Various compounds containing aromatically bonded nitrogen have already been proposed as activators to increase test sensitivity. Quinoline derivatives are described in DE-AS Nos. 12 42 905, DE-AS 22 35 152, DE-AS 26 40 211, isoquinoline derivatives in DE-AS 25 48 279, thiazole derivatives in DE-OS No. 26 52 545, and certain pyridine derivatives in DE-OS No. 23 63 344. In Published European Patent Application No. 0 021 407 substituted or condensated pyridines, preferably azafluorene or indenopyridine, are mentioned as activators or accelerators.